Method for acquisition of exhalation tidal volume and minute ventilation data

ABSTRACT

An exhalation tidal volume and minute ventilation data acquisition method for application to and use with a pressure breathing inhalation therapy ventilator for use by humans. The device for practicing the method comprises a substantially inelastic flexible collapsible vessel of known volume for attachment to the exhaust valve of the pressure breathing assistor in inhalation therapy, the vessel filling with exhaled air so that, when the number of breaths and time for vessel filling are determined, the tidal volume and minute ventilation are established. The method comprises collecting exhaled air in a substantially inelastic flexible collapsible vessel of known volume and counting the breaths and/or time required to fill the vessel so that exhalation tidal volume and minute ventilation are determined.

Unite States Ptet n91 Yanda Dec.2, 1975 1 METHOD FOR ACQUISITION OF EXI-IALATION TIDAL VOLUME AND MINUTE VENTILATION DATA [76] Inventor: Roman L. Yanda, 15423 Vanowen St., Van Nuys, Calif. 91405 22 Filed: Aug. 12,1974

211 App]. No.: 496,410

Related US. Application Data [63] Continuation of Ser. No. 401,577, Sept. 28, 1973, abandoned, which is a continuation of Ser. No. 120,980, March 4, 1971, abandoned.

[52] US. Cl. l28/2.08 [51] Int. Cl. A61B 5/08 [58] Field of Search 128/208, 2.07

[56] References Cited UNITED STATES PATENTS 225,710 3/1880 Marsh 128/208 327,403 9/1885 McDonnell... 128/208 392,711 11/1888 Barton 128/208 1,684,221 9/1928 Gougnard 128/208 1,781,735 11/1930 Scott 128/208 2,999,495 9/1961 Shipley 128/208 3,395,699 8/1968 Beasley 128/208 3,426,745 2/1969 Farr 128/207 X 3,467,078 9/1969 Bird et al. 128/208 3,507,271 4/1970 Reiner 128/208 FOREIGN PATENTS OR APPLICATIONS France 128/208 France 128/208 United Kingdom 128/208 OTHER PUBLICATIONS The Lancet, Feb. 13, 1960, p. 369.

Primary Examiner-Kyle L. Howell Attorney, Agent, or Firm-Herzig & Walsh Incorporated [57] ABSTRACT An exhalation tidal volume and. minute ventilation data acquisition method for application to and use with a pressure breathing inhalation therapy ventilator for use by humans. The device for practicing the method comprises a substantially inelastic flexible collapsible vessel of known volume for attachment to the exhaust valve of the pressure breathing assistor in inhalation therapy, the vessel filling with exhaled air so that, when the number of breaths and time for vessel filling are determined, the tidal volume and minute ventilation are established.

The method comprises collecting exhaled air in a substantially inelastic flexible collapsible vessel of known volume and counting the breaths and/or time required to fill the vessel so that exhalation tidal volume and minute ventilation are determined.

2 Claims, 3 Drawing Figures US. Patent Dec. 2, 1975 BREA HS TIDAL VOL.

mcaqmm-Pwn- SECS. To MINUTE FILL VENT v FULL CARY j 4c RommJ L. YQAJ'bA? I N VEN TOR.

wan

METHOD FOR ACQUISITION OF EXIIALATION TIDAL VOLUME AND MINUTE VENTILATION DATA RELATED APPLICATIONS This application is a continuation of my co-pending application Ser. No. 401,577, filed Sept. 28 1973, now abandoned which application in turn was a continuation of co-pending application Ser. No. 120,980 filed Mar. 4 1971, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is directed to a method for acquiring data related to the exhalation tidal volume and minute ventilation of human beings employing a pressure breathing assistor in inhalation therapy.

2. Description of the Prior Art Several human disorders cause human breathing limitations which are aided by inhalation therapy which includes employment of a pressure breathing assistor. Such disorders include emphysema and asthma. Several pressure breathing assistors for such inhalation therapy are available on the commerical market and in general use in hospitals and clinics. In general, these devices comprise an oxygen or air pressure supply, and a valve which responds to negative pressure in a patientsmouthpiece to deliver pressurized air or oxygen from the supply to the patients lungs, and subsequently permit exhalation by the patient through the mouthpiece and out of a valve exhaust port to the atmosphere. As used herein, it will be readily appreciated and understood by those persons dealing with this art that the term air may include various vapors, inhalants, gases and so forth, as the context or art requires.

The valve which thus alternately connects the pressure supply to the patients tube, or connects the mouth tube to exhaust to atmosphere is the critical element of the pressure breathing assistor device. Several valves are commercially available and each, of course, responds to the pressure in the mouthpiece which, in turn, corresponds to pressure in the lungs.

A nebulizer is often attached or attachable to the valve so that aerosol medication can be provided to the patient during inhalation. All medication requires correct dosage and, in the case of inhalation therapy, the dosage is computed on the basis of volume and patient size. Tidal volume is the normal breath volume of the lungs, usually given in liters, while minute ventilation or minute volume are interchangeable terms conventionally employed by those who work in this art to signify the amount of air exhaled from the lungs in one minute of normal breathing, usually given in liters per minute. When this data is obtained, proper medication dosage can be prescribed for the individual patient.

Several prior devices have been developed in an attempt to acquire this necessary data for medication and settings of the pressure breathing assistor equipment. The first of these devices is in the nature of a turbine where the rotor turns under the influence of tangential air flow, which air flow is the breath exhaust. The rotor is mounted on jewel bearings and is turned by the passing air at a speed proportional to the air flow through the instrument. A gear train, similar to that of a watch, connects the rotor to the hands on a dial. A serious disadvantage of this meter is its fragility. Great care must be taken to avoid accidental damage. Additionally, the

accuracy of this meter depends on whether the flow is steady, or upon the waveform of the air flow, and on the magnitude of the flow. Normally, such a meter tends to overread at high ventilation rates and under read at low ventilation rates.

The above-described ventilation meter is not positive in that air can flow therethrough without resulting in an exactly corresponding motion of the meter parts. Positive devices are also available in the prior art. In one case, a pair of intermeshing gears are mated in a closefitting housing. In another, interengaging lobes are rotatbly mounted in a closefitting housing. In either case, the flow of air through the housing positively causes rotation. Such meters respond to flow in both directions. Dials are connected to the shafts to indicate the amount of air that is passed. These meters must be carefully made to turn under the influence of pressure drop as low as a few centimeters of water in order to have a low respiratory resistance. Thus, they are also sensitive to physical damage.

Another type of breath volume measuring device heretofore incorporated into pressure breathing assistors or ventilators employs high negative pressure air from the air source. This type of measuring device is a convoluted bellows device of maximum flexibility. It is connected to valving such that it receives the patients exhaled air and, when an exhaled breath is completed, the bellows has the air discharged therefrom. Since this bellows device employs high negative pressure air, it must necessarily be inter-related to the high pressure air supply device. Furthermore, its valves are delicate, but must be responsive to extremely low pressures and, thus, provide an additional reliability problem.

SUMMARY OF THE INVENTION In order to aid in the understanding of this invention, it can be stated in essentially summary form that it is directed to an exhalation tidal volume and minute volume data acquisition method. The device for practicing the method comprises a substantially inelastic flexible vessel of substantially known volume which is attachable to the outlet of a human inhalation therapy device. The method comprises the employment of such a vessel and counting the number of breaths and/or time it takes to fill the vessel, so that the tidal volume and/or the ventilation volumes are established.

It is, thus, an object of this invention to provide an exhalation tidal volume and/or minute ventilation data acquisition method. It is a further object to provide, for practicing the method, a vessel formed of flexible and substantially inelastic material which can be inflated, the maximum inflation volume of which is known so that, as it is inflated by breath exhalation of the patient, tidal volume and minute ventilation can be determined by counting breaths and time to fill the flexible vessel. It is another object to provide, for practicing the method, a bag of flexible and substantially inelastic naterial which is inflatable and is employed by attaching the uninflated bag to the patients breath exhaust from an inhalation therapy device so that exhaled air is collected and the bag is filled by successive breaths of the patient, so that data can be acquired with respect to tidal volume and minute ventilation. It is a further object to provide a method whereby exhalation tidal volume data and/or minute ventilation data are acquired by positioning an inflatable bag of substantially inelastic character and known volume onto the exhaust of the valve from which issues the patients exhaled air, and counting breaths and/or measuring the time it takes to inflate the bag so that average tidal volume and average minute ventilation are known.

Still other objects, features and attendent advantages of the present invention, together with modifications, will become apparent to those skilled in the art from a reading of the following detailed description of the preferred embodiments, constructed in accordance therewith, taken in conjunction with the accompanying drawings wherein like numerals designate like parts in the several figures.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the exhalation tidal volume and ventilation data acquisition device wherein the device is shown in broken lines in its initial, relaxed condition and in solid lines when distended by virtue of being filled to capacity.

FIG. 2 is a fragmentary enlarged view, partly broken away, showing the otherwise-open end of the device secured on the valve, as by an elastic band.

FIG. 3 is a plan view of the device, showing data table printed thereon and being partly broken away to show the closed and open ends.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates an inhalation thereapy pressure breathing assistor, with the exhalation tidal volume and ventilation data acquisition device of this invention attached to its valve, in association with a patient. The inhalation therapy device comprises a pressure supply 10 which delivers a supply of breathing air, possible enriched with oxygen, through pressure tube 12. The pressure supply device has suitable controls for maintaining the pressure at the proper level. It may also have sensing devices therein for indicating when the pressure supply device is not operating correctly or for sensing and indicating other conditions.

Pressure tube 12 delivers air under pressure to valve 14 through an inlet connection 16 on the valve. Patient 18 has a mouthpiece 20 which is mounted upon mouthpiece connection 22 on valve 14. Valve 14 us a conventional structure of the prior art and is known in connection with the usual respiration units.

As described, pressure supply device 10 supplies the air, optionally enriched with oxygen, under pressure to valve 14. Valve 14 is of such nature that, when the patient draws upon the mouthpiece to reduce the pressure therein below a predetermined point, the valve 14 opens to connect inlet 16 to mouthpiece 20 so that pressurized air passes into the patients mouth to ventilate the patient to thus act as a pressure breathingassistor. When the pressure in mouthpiece 20 rises to a certain predetermined point, the valve 14 closes to cutoff further inlet of pressurized air into inlet connection 16 to permit the patient to exhale. Exhalation takes place through exhaust port 24 on the side of the valve 14. Normally, the exhaust port is equipped with a one-way valve or check valve which only permits exhaust or outlet from this port. When exhalation is complete, the pressure in mouthpiece 20 drops below the set point, so that another breathing cycle begins.

Conventionally, a nebulizer 26 is attached or can be attached to the valve 14 so that medication can be introduced into the inhaled air. Such application of the nebulizer is desirable, so that medication is only delivered when there is air flow in the inhalation direction through mouthpiece 20. It is essential that the tidal volume and minute ventilation of the patient be known, in order to properly prescribe and adjust medication flow.

The exhalation tidal volume and minute ventilation data acquisition device of this invention is generally identified at 28. The device comprises an inflatable, collapsible, substantially impermeable, substantially inelastic bag of flexible material, the bag having a known volume. The bag is of preferably tubular construction and has an open end 30, as well as a closed end 32. Conveniently, it is extruded of common thermoplastic synthetic polymer composition material such as vinyl or polyethylene, and suitably cut and closed.

In use, the device 28 has its open end attached over the exhaust port 24 of valve 14, and it is sealed with respect thereto by any convenient means, such as rubber band 34. When installed, the bag is empty and hangs in the limp collapsed position shown in dotted lines in FIG. 1. Thereupon, the patient takes the mouthpiece 20 and breathes in his normal way, each exhalation causing partial inflation of bag 28 until successive exhalations have cumulatively filled the bag. The therapist in charge counts the breaths and takes the time interval from the beginning of breathing to the time the device 28 is full. It will be noted that, with the preferred tubular construction, the vessel 28 assumes a substantially rigid distended condition only when filled so that its fully inflated status is visually apparent as a signal to the therapist at the instant of occurrence. Thereupon, the device 28 can be stripped off of the valve 14, so that the patient can continue normal pressure-assisted breathing, in accordance with the therapy, and the device can be permitted to collapse.

The full capacity of the device 28 is known and is preferably marked thereon, as at 36. It is only necessary to divide the number of breaths into this full capacity in order to find the tidal volume. In order to assist the therapist in this division, the table can be provided, as shown by the indicia 38. Thes indicia show the tidal volume in liters per breath. Finally, should the therapist wish to know the minute ventilation, he only need divide the capacity of the device by the time it required to fill the device 28. In order to aid the therapist in this calculation, markings 40 are provided to indicate the minute ventilation in liters per minute, commonly known by the symbol V, as a function of the seconds to fill the vessel 28. From this data, the condition of the patient is further known, to aid diagnosis, and to provide essential data for prescription and treatment. This is accomplished with the device 28 which is inexpensive but has a reliable construction of such nature that the operator can readily observe that the device is operating correctly. Furthermore. several consecutive tidal volume and minute volume tests can be made and averaged, should closer tolerance accuracy be re quired. Inherent in the device is the low respiratory re sistance, which aids the patient and provides for the required accuracy.

It is also seen that the device comprises a disposable bag, because of its inexpensive character. Since manufacture of such devices can be accomplished in sterile manner, no further sterilization is necessary. In addition, because it is disposable, it need not be sterilized between uses. Since the bag meters and collects a measured quantity, it accurately measures the quantity involved. Accuracy is enhanced by such collection so that testing and treating in inhalation therapy is accurately accomplished.

The tidal volume and ventilation data acquisition device and method has been described in connection with a particular type of inhalation therapy equipment. All inhalation therapy equipment must have an exhaust-toatmosphere and such exhausts are normally equipped with one-way valves or check valves, which permit breath flow only in the direction from the equipment to atmosphere. It is on such exhausts in any type of inhalation therapy equipment that the device of this invention can be employed for the practice of this method.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

I claim:

1. The method of measuring the exhalation tidal volume of a patient comprising the steps of:

selectively connecting a fully collapsed flexible inelastic bag to a respirator to receive substantially all the exhaled breaths of a patient, said bag having a volume of substantially zero when fully collapsed and a selected known volume when fully inflated; accumulating all the exhaled breaths of said patient in said bag until said bag is fully inflated; and providing on said bag a table of tidal volumes with respect to numbers of exhaled breaths necessary to fully inflate the bag whereby tidal volume can be read from the table based on the number of exhaled breaths necessary to inflate the bag. 2. The method of measuring the exhalation minute ventilation of a patient comprising the steps of:

selectively connecting a fully collapsed flexible inelastic bag to a respirator to receive substantially all the exhaled breaths of a patient, said bag having a volume of substantially zero when fully collapsed and a selected known volume when fully inflated; accumulating all the exhaled breaths of said patient in said bag until said bag is fully inflated; and providing on said bag a table of minute ventilation values with respect to numbers of seconds to till the bag whereby minute ventilation can be read from the table based on the number of seconds to fill the bag. 

1. The method of measuring the exhalation tidal volume of a patient comprising the steps of: selectively connecting a fully collapsed flexible inelastic bag to a respirator to receive substantially all the exhaled breaths of a patient, said bag having a volume of substantially zero when fully collapsed and a selected known volume when fully inflated; accumulating all the exhaled breaths of said patient in said bag until said bag is fully inflated; and providing on said bag a table of tidal volumes with respect to numbers of exhaled breaths necessary to fully inflate the bag whereby tidal volume can be read from the table based on the number of exhaled breaths necessary to inflate the bag.
 2. The method of measuring the exhalation minute ventilation of a patient comprising the steps of: selectively connecting a fully collapsed flexible inelastic bag to a respirator to receive substantially all the exhaled breaths of a patient, said bag having a volume of substantially zero when fully collapsed and a selected known volume when fully inflated; accumulating all the exhaled breaths of said patient in said bag until said bag is fully inflated; and providing on said bag a table of minute ventilation values with respect to numbers of seconds to fill the bag whereby minute ventilation can be read from the table based on the number of seconds to fill the bag. 